Wurtzite Structure Research Articles

Highly sensitive electrochemical sensor for glutathione detection using zinc oxide quantum dots anchored on reduced graphene oxide

This work presents a highly sensitive and selective electrochemical sensor for glutathione (GSH) detection using a glassy carbon (GC) electrode modified with zinc oxide quantum dots-reduced graphene oxide nanocomposites (ZnO QDs-rGO NCs). The ZnO QDs (diameters about ∼2 to 8 nm) were synthesized and successfully anchored onto the surface of reduced graphene oxide (rGO). The resulting nanocomposites were then characterized using various spectroscopic and microscopic techniques. The wurtzite crystal structure of ZnO and anchored onto the rGO surface were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synergistic interaction between ZnO QDs with rGO provides a large surface area, high conductivity, and efficient transfer of electrons, resulting in improved electrocatalytic activity for GSH oxidation. The ZnO QDs-rGO/GC electrode exhibits exceptional performance with a wide linear range (0.01–10 μM), high sensitivity (3.66 μAμM−1), and excellent selectivity for GSH. The sensor demonstrates good analytical stability, characterized by high reproducibility (%RSD = 2.90%) and repeatability (%RSD = 1.49%), and maintains its performance in the presence of common biological interferences. The applicability of the sensor was validated through successful GSH detection in complex matrices like human blood and pharmaceutical capsules, achieving recovery rates of 98.1-102.0% with excellent reliability.

Influence of cobalt doping on structural, optical, and electrical properties of zinc oxide nanoparticles prepared by polymeric precursor method

Cobalt-doped ZnO nanoparticles at different compositions have been obtained by the polymeric precursor method. The nanoparticles were obtained at the working pH from 8.3 to 8.5 and synthesized at 550 °C. The properties were studied using X-ray diffraction (XRD), vibrational spectroscopy (FTIR/Raman), diffuse reflectance absorbance spectroscopy (DR UV–Vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM/EDS), and impedance spectroscopy. The lattice parameters were determined at room temperature by Rietveld refinement, confirming single-phase composition with a hexagonal wurtzite structure. FTIR and Raman analyzes identified the characteristic vibrations of the synthesized system and the typical deformations of the wurtzite-type hexagonal structure, corroborating the results obtained from XRD. A redshift in the optical energy band gap (Egopt) was observed with increasing cobalt content compared to the ZnO sample. Considering the doping percentage, Egopt value varied between 3.13 eV and 3.04 eV for pure ZnO and Co-doped ZnO with 5 at. %., indicating that the optical properties of the nanoparticles were affected by dopant concentration. PL and SEM/EDS characterization were used to determine the associated defects for each sample and the morphology and composition of the nanoparticles. PL results showed a strong blue emission at around 439 nm (2.83 eV), which is redshift with cobalt content (ΔE between 0.05 eV and 0.01 eV), attributed to the surface defects present in the doped samples. Conductivity analysis to temperature revealed a semiconductor behavior for all samples, and their respective activation energies determined. The results provide an easy method to obtain Co-doped ZnO nanoparticles with interesting properties for optoelectronics devices.

Defect-controlled fabrication of reduced graphene oxide/ZnO/PMMA-based solid-state optical limiting filters with SA/RSA switching property

A solid-state optical limiting filter was fabricated by noncovalently functionalizing a graphene-based nanocomposite with a polymer. Graphene oxide was reduced by varying reducing agent concentration and functionalized with metal oxide nanoparticles to enhance electronic transitions and third-order nonlinear optical characteristics. The nanocomposite was dispersed over the PMMA polymer framework, and thin films with μm-scale thickness were fabricated using the dip coating method. XRD analysis confirmed the wurtzite crystal structure of ZnO nanoparticles and the amorphous nature of PMMA. The carbon structural integrity was analyzed using Raman spectra. Linear optical studies revealed a redshift in the π-π* transition peak in rGO, suggesting enhanced conjugation. Third-order nonlinear refraction and absorption properties were assessed using the Z-scan technique, revealing a switching behavior in nonlinear absorption at different input intensities. An increase in the relative concentration of sp2 domains enhanced the nonlinear absorption. Optical limiting potential, determined using open aperture Z-scan data, yielded a threshold value of 0.066 GW/cm2. This study aims to develop a solid-state optical filter with a high laser damage threshold by adjusting the reduction rate, tuning defect levels, and analyzing its effect on the optical limiting potential.

Enhanced photodegradation of textile dye wastewater using silane/polymer doped ZnO nanocomposites and antibacterial activity

Accumulation of textile dye wastewater is major global issue that causes negative impact to the ecosystem. This study focuses on industrial textile dye effluent treatment by photodegradation, and degradation of Malachite green dye under sunlight, visible and UV light. ZnO demonstrated hexagonal wurtzite structure with average crystallite size 38 nm for ZnO/PEG, 21 nm for ZnO/PEG/VTES and 17 nm for ZnO/PEG/VTMS. Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy revealed nanometer sized particles and purity. Bandgap energy and particle size of ZnO/PEG/VTMS is 102 nm and 3.134 eV is lesser than ZnO/PEG (147 nm, 3.181 eV) and ZnO/PEG/VTES (109 nm, 3.151 eV). Photoluminescence analysis revealed reduced recombination rate of ZnO/PEG/VTMS. Antibacterial efficacy of ZnO/PEG/VTMS was tested against Staphylococcus aureus (35 mm) and Escherichia coli (29 mm). Photodegradation of textile dye wastewater by ZnO/PEG/VTMS under visible and UV light exposure revealed an effective way for textile dye effluent treatment, which maintained its efficiency even after five photodegradation cycles.

The figure of merit improvement of (Sn, Co)–ZnO sprayed thin films for optoelectronic applications

Nanocrystalline zinc oxide (ZnO) has garnered significant attention from researchers and industries due to its superior properties as an optoelectronic material, particularly in solar cells as a transparent electrode. Doping, especially with tin (Sn) and co-doping with tin and cobalt (Co), can refine its optoelectronic properties. In this manuscript, we report on the optoelectronic properties of undoped ZnO thin films, as well as those doped with Sn and/or Co, elaborated using a simple chemical pneumatic spray pyrolysis method on glass substrates. A 1 % Sn doping concentration was used, with Co doping concentrations of 0 %, 0.5 %, and 1 %. The effects of Sn and/or Co doping concentration on the structure, morphology, optical, and electrical properties of nanocrystalline ZnO were studied using X-ray diffractometer (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FESEM), UV–Vis–NIR spectroscopy and Hall effect measurements. All the films studied exhibit wurtzite ZnO structures with a predominant (002) orientation and no secondary phase, as confirmed by X-ray diffraction (XRD) analysis. The Raman spectroscopy also reveals the presence of a wurtzite structure in all the films. The FESEM images reveal the kind and concentration of the dopants significantly influenced the surface morphology of the films. The elemental analysis with energy dispersive X-ray analysis (EDS) analysis successfully detected the doping of Sn and Co. The analysis of UV–Vis spectroscopy provide that the optical band gap for the undoped ZnO film is 3.25 eV. This band gap increases upon doping and co-doping, reaching a peak value of 3.30 eV for the Sn:Co (1 %:0.5 %) co-doped ZnO film. The ZnO film shows an improvement in the electrical resistivity upon doping and co-doping with low resistivity value of 1.95 × 10−2 Ω cm for the film (1%Sn, 0.5 % Co)–ZnO. The highest figure of merit (FOM) achieved is 1.41 × 10−4 Ω−1 for a ZnO thin film co-doped with (1 % Sn, 0.5 % Co). The existence of (1 % Sn, 0.5 % Co) film with improved optical gap, low electrical resistivity and high FOM supports its use in transparent conductive oxide applications.

Investigation of zinc oxide doped microstructures with cobalt via electrochemical deposition

The present paper reports electrochemical elaboration of zinc oxide microstructure doped with cobalt (CZO) at various [Co2+]/[Zn2+] (Co/Zn) concentration ratios onto ITO substrates at a pH of 6.5. All Mott-Schottky plots of electrochemical analysis showed that all electrodeposited CZO samples exhibited n-type semiconducting behaviours. XRD spectra revealed that all electrodeposited CZO samples crystallized in the typical hexagonal wurtzite structure with a preferential orientation along the (100) plane with descending crystalline size versus increasing cobalt dopants amount. Reviewing SEM images, notable changes were found on granular morphologies of CZO samples because of doping changing. EDX showed proportionality between the increase of final Co/Zn ratio in the CZO samples and the increase of starting Co/Zn concentration ratio within the initial depositing solutions. UV–Vis measurements indicated that transmittances of most CZO samples were above 80 % in the visible range and their optical band gaps were high and limited between 3.60 and 3.64 eV.

Microstructural and optoelectronic properties of sputtered Al:ZnO films and Al:ZnO/Cu bilayer structures: Effects of substrate and Cu thickness

In this study, using a multi-source confocal radio frequency magnetron sputtering system, we synthesized aluminum doped zinc oxide (AZO) single layers and AZO/Cu bilayers on glass and crystalline quartz substrates with a constant AZO thickness of 65 nm and variable Cu bottom layers with a thickness of 4–13 nm. The microstructural, morphological, optical, and electrical characteristics of all samples were investigated using a variety of spectroscopic techniques. The X-ray diffraction results show that all films prepared on both substrates have a hexagonal wurtzite crystal structure and exhibit the preferred orientation along the (002) plane with some microstructural variations. The atomic force microscopy images revealed that the thickness of the Cu layer and substrate type greatly affect the films' topography and surface roughness. The transmittance spectra indicate that the single AZO layer on both substrates possess the highest average visible transmission; however, all the samples deposited on glass substrates show greater transmittance than that on quartz. Photoluminescence analysis put into evidence a decrease in ultraviolet emission with Cu thickness for both substrates, with intensities varying according to substrate type. Hall Effect measurements reveal that all samples have n-type conductivity as well as that Cu thickness has a significant impact on their electrical characteristics. Moreover, a higher value of the figure of merit is achieved with the AZO/Cu bilayer structure grown on a glass substrate with 13 nm of Cu layer thickness.

La:ZnO nanoparticles: an investigation on structural, optical, and microwave properties

This paper presents the utilization of ethylene glycol monomethyl ether (EGME) during the synthesis of ZnO and La:ZnO with two tasks as a solvent and a fuel source within the gel combustion technique. The use of EGME for this purpose provides one-step production of the nanoparticles (NPs) and saves a considerable amount of time. The detailed characterization of the nanoparticles was carried out by X-ray diffractometer (XRD), scanning electron microscope (SEM), particle size analyzer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Vector Network Analyzer (VNA) measurements, respectively. The NPs exhibited a hexagonal wurtzite structure with good crystallinity and a porous spongy morphology. The photoluminescence emission maxima of the synthesized NPs appeared at 500, 560, and 676 nm, upon excitation by the 372 nm of excitation. La:ZnO NPs showed significantly better photoluminescent characteristics than La-free ZnO forms. When excited at the same wavelength, La-free ZnO, 3%, and 7% La:ZnO exhibited 92, 45, and 35 μs average decay times, respectively. Finally, the microwave properties of the relative complex permittivity and permeability characteristics were also investigated and discussed in detail, which were derived from the scattering parameters of S11 and S21 in the X band regime.

Investigation of the Structural, Electrical, and Optical Properties of Co-Precipitation-Synthesized Aluminum-Doped ZnO Nanostructures

Abstract: This study examines the Structural, Electrical, and Optical characteristics of Zinc Oxide substituted with aluminum (AlxZn1-xO; x = 0, 0.02, 0.04, 0.06, 0.08). The coprecipitation technique is used to synthesize the powders, and X-ray diffraction (XRD) is used to analyze the powders' structural properties. Field Emission Scanning Electron Microscopy (FESEM) is used to study the morphological characteristics of the produced powders. The UV-visible absorbance spectrum (UV-Vis.) was used to assess the particles' optical characteristics. Using photoluminescence (PL) spectra, the effects of morphology on the optical and electrical characteristics of produced powders were examined. The XRD patterns verified that a single-phase hexagonal wurtzite structure formed for each sample. The powders' FESEM pictures reveal how, as the Al concentration increases, the particles' morphology alters from hexagonal to spherical. The synthesized samples have crystallite sizes between 19 and 26 nm. The predictable variations noticed with Al3+ concentration are consistent with Al3+ incorporation into the ZnO lattice, as confirmed by the UV-Vis spectroscopy measurements.

Green Synthesis of ZnO Nanostructures and Their Antibacterial Activity Against Catfish Pathogen

Due to its antibacterial activity against clinical bacterial pathogens at the time of tissue development, zinc oxide (ZnO) is considered one of the most important metal oxide nanostructured materials. In this study, ZnO nanostructures were prepared using Aloe vera gel juice, which is easy, inexpensive, and ecofriendly. The nanostructures of ZnO were characterized using a variety of analytical techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and dynamic light scattering (DLS). As a result of the XRD study, the hexagonal phase of ZnO with the structure of wurtzite has been identified. ZnO material with high heterogeneity morphology has been observed by SEM analysis. As-prepared ZnO nanostructures were tested for their antibacterial activity against the newly discovered pathogen of catfish. A ZnO sample prepared with a high concentration of Aloe vera gel possessed an inhibition zone of 13.21±0.04 mm, whereas a ZnO sample prepared with a low concentration of Aloe vera juice had an inhibition zone of 6.23±0.02 mm and a pure ZnO sample had an inhibition zone of 3.31±0.03 mm. Furthermore, we examined the effectiveness of the ZnO nanostructures on bacterial strains based on the type of nanoparticles applied to the commercial strains. In addition to their modified surface properties, small particle size, and highly toxic effects for the killingof bacterial cell growth, the Aloe vera juice assisted ZnO nanostructures demonstrated excellent antibacterial activity against the catfish pathogens.

The role of oxygen vacancies in enhancement of photocatalysis and ferromagnetism of (Mn, Co) co-doped ZnO nanoparticles

(Mn, Co) co-doped ZnO nanoparticles (NPs) were synthesized using the sol-gel method. Rietveld refined XRD patterns indicated that the NPs exhibited hexagonal wurtzite structures. Co and Mn ions were successfully introduced into the ZnO NPs at different concentrations. Moreover, Raman peak at 520 cm−1 was related to the defects induced by doping with Mn and Co ions. Fitting the O 1s XPS spectra of the NPs showed that more oxygen vacancies formed with increasing Co and Mn doping. Because there were more oxygen vacancies, photocatalytic dye degradation of rhodamine B enhanced at higher Co and Mn concentrations. Photoluminescence spectra showed that the NPs containing more Mn and Co had more single charged oxygen vacancies. The experimental and theoretical results showed that the exchange interactions between the Mn2+-Co2+ ions mediated by singly charged oxygen vacancies was responsible for room temperature ferromagnetism in the (Mn, Co) co-doped ZnO NPs.

Tuning of structural, magnetic, and optical properties of ZnO nanoparticles by Co and Cu doping

Undoped, Cu, and Co-doped ZnO nanoparticles were synthesized by a simple co-precipitation method. We studied the structural, chemical, magnetic, and optical properties of synthesized nanoparticles by using X-ray Diffraction, Fourier Transform Infrared, Scanning Electron Microscopy, Vibrating-Sample Magnetometer, and UV–VIS spectroscopy. The X-ray Diffraction analysis discovers the crystalline hexagonal wurtzite structure and confirms the incorporation of Cu2+ and Co2+ in the ZnO lattice. The SEM photographs show that the nanoparticles are agglomerated, and the grain size of pure ZnO is decreased upon doping, showing inhibition of grain growth through doping. From VSM the coercivity and saturation magnetization of Co-doped (0.0189 emu/g and 84.044Oe) is higher as compared to pure and Cu-doped ZnO. The energy gap of doped and un-doped nanoparticles determined from the absorption spectrum indicates that it increases by doping of Copper and cobalt.

Efficient rhodamine B dye photocatalytic degradation in aqueous media using novel ZnO nanomaterials co-doped with Ce and Dy

Water pollution caused by dyes and industrial wastewater poses a significant threat to ecosystems. The purification of such pollutants presents a major challenge. Photocatalysis based on semiconductor materials is a potential wastewater treatment process due to its safety and cost-effectiveness. In the present work, Zn1-2xCexDyxO (x = 0.01–0.05) semiconductors were prepared by the sol-gel auto-ignition method. The samples are denoted CDZO1, CDZO3, and CDZO5 for x = 0.01–0.05, respectively. The X-ray diffraction and Raman spectroscopy results revealed the formation of ZnO hexagonal phase wurtzite structure for all synthesized compositions. Different structural properties were determined. It was found that the lattice parameters and the unit cell volume increased, while the crystallite size diminished as x varied from 0.01 to 0.05. Transmission electron microscopy observations confirmed the formation of nanoparticles with the desired chemical compositions. The specific surface area (SSA) values are found to be 39.95 m2/g, 48.62 m2/g, and 51.36 m2/g for CDZO1, CDZO5, and CDZO5 samples, respectively. The reflectance spectra were recorded to examine the optical properties of the different nanoparticles. The values of the optical band gap were 3.221, 3.225, and 3.239 eV for CDZO1, CDZO3, and CDZO5 samples, respectively. In addition, the photocatalytic performance towards RhB dye degradation for the different samples was assessed. It was established that the CDZO3 sample with a moderate SSA value exhibited the superior photocatalytic performance among the other as-prepared samples wherein the percentage of degradation efficiency, and kinetic constant rate attained their maximum values of 98.22 % and 0.0521 min−1, respectively within 75 min. As per the obtained findings, it is evident that the Zn1-2xCexDyxO photocatalyst has prominent potential for use in the degradation of dyes and offers a useful route for impeding the recombination of electron-hole pairs of zinc oxide material.

Green marvel: Harnessing spinach leaves' power for enhanced photodegradation of various effluents with biogenic ZnO nanoparticles

This study investigates the use of ZnO NPs (Zinc oxide nanoparticles) derived from spinach leaf extracts in a sustainable photocatalytic technology to enhance the decomposition of hazardous effluents from refineries and paper mills. The biosynthesized ZnO NPs were characterized through X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD analysis reveals that ZnO NPs possess a hexagonal wurtzite structure, exhibiting a preferred arrangement of (101) planes. The synthesized ZnO NPs have a spherical shape, as seen in the SEM images. TEM analysis detected the size of the ZnO NPs to be between 35 and 40 nm. The results indicate that ZnO NPs produced via biosynthesis have photocatalytic activity in efficiently decomposing the organic chemicals found in gasoline refining effluent when exposed to light. At a pH of 8, the ZnO NPs exhibited the highest rate of degradation for toluene (84.26 %) and xylene (90.36 %) after being exposed to simulated sunlight for 240 min. In the context of the photocatalytic treatment of paper mill effluents, it has been shown that the subsequent cycles resulted in a reduction in chemical oxygen demand (COD) levels of 81.24 %, 74.14 %, 68.92 %, 60.24 %, and 53.82 %, respectively.

Harnessing Walnut-Based Zinc Oxide Nanoparticles: A Sustainable Approach to Combat the Disease Complex of Meloidogyne arenaria and Macrophomina phaseolina in Cowpea.

Zinc oxide nanoparticles (ZnO NPs) exhibit diverse applications, including antimicrobial, UV-blocking, and catalytic properties, due to their unique structure and properties. This study focused on the characterization of zinc oxide nanoparticles (ZnO NPs) synthesized from Juglans regia leaves and their application in mitigating the impact of simultaneous infection by Meloidogyne arenaria (root-knot nematode) and Macrophomina phaseolina (root-rot fungus) in cowpea plants. The characterization of ZnO NPs was carried out through various analytical techniques, including UV-visible spectrophotometry, Powder-XRD analysis, FT-IR spectroscopy, and SEM-EDX analysis. The study confirmed the successful synthesis of ZnO NPs with a hexagonal wurtzite structure and exceptional purity. Under in vitro conditions, ZnO NPs exhibited significant nematicidal and antifungal activities. The mortality of M. arenaria juveniles increased with rising ZnO NP concentrations, and a similar trend was observed in the inhibition of M. phaseolina mycelial growth. SEM studies revealed physical damage to nematodes and structural distortions in fungal hyphae due to ZnO NP treatment. In infected cowpea plants, ZnO NPs significantly improved plant growth parameters, including plant length, fresh mass, and dry mass, especially at higher concentrations. Leghemoglobin content and the number of root nodules also increased after ZnO NP treatment. Additionally, ZnO NPs reduced gall formation and egg mass production by M. arenaria nematodes and effectively inhibited the growth of M. phaseolina in the roots. Furthermore, histochemical analyses demonstrated a reduction in oxidative stress, as indicated by decreased levels of reactive oxygen species (ROS) and lipid peroxidation in ZnO NP-treated plants. These findings highlight the potential of green-synthesized ZnO NPs as an eco-friendly and effective solution to manage disease complex in cowpea caused by simultaneous nematode and fungal infections.

Green and chemical synthesized zinc oxide nanoparticles: Evaluation of their anti-proliferative activity against breast cancer cell line – An in vitro and in silico approach

Zinc Oxide nanoparticles (ZnO NPs) were synthesized through both chemical and green approaches using wheat grass (WG) extract. Characterization techniques included Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDX), Fourier-transform infrared Spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-visible (UV-Vis) spectroscopy. CS-ZnO NPs and WG-ZnO NPs exhibited characteristic surface plasmon resonance (SPR) peaks at 360 nm and 320 nm, respectively, with low polydispersity index (PDI) values indicating uniform nanoparticle dispersion. FTIR analysis revealed distinct functional groups on the ZnO NPs’ surface for stabilization. XPS confirmed atomic composition and oxidation state, while XRD confirmed their hexagonal wurtzite structure. SEM images revealed rod-shaped structures, supported by EDX analysis confirming ZnO NP formation through elemental content. The synthesized ZnO NPs demonstrated significant cytotoxicity against MDA-MB 231 breast cancer cells, causing changes in nuclear morphology, increased reactive oxygen species levels, and membrane damage. Wound healing assay highlighted their potential in inhibiting cancer metastasis. Molecular docking between WG compounds and breast cancer targets revealed that the enhanced efficacy of green-synthesized ZnO NPs could be attributed to covalent linkage of active molecules of WG onto the nanoparticle surface. Overall, ZnO NPs synthesized using the green method outperformed their chemically synthesized counterparts.

Impact of aliovalent La-doping on zinc oxide – A wurtzite piezoelectric

The development of high-performance low-cost electroactive films for energy conversion and electronic device applications is a key goal of current advanced materials and condensed matter physics research. Here, using solution-based scalable chemical spray pyrolysis, high-quality electroactive lanthanum-doped zinc oxide (i.e., Zn1-xLaxO) thin films are grown on silicon substrates, and the impact of aliovalent lanthanum doping is investigated using a suite of microstructural, optical and nanoscale scanning probe microscopy techniques. The synthesized polycrystalline thin films show hexagonal wurtzite crystal structure with an increased unit cell volume, crystallite size, and conductivity with lanthanum doping up to 4 at.% beyond which the thin films (6 at.%), however, exhibit a change in dominant crystalline orientation from (101) to (002) plane. Concurrently, at this optimal dopant concentration of 4–6 at.%, the electromechanical performance is enhanced by about 20 %, and polarity-dependent nanoscale electronic transport behaviour is revealed. Our study, therefore, provides key insights into the impact of the rare earth aliovalent lanthanum dopant on the electroactive and electronic properties of low-cost, functional thin films for sustainable energy and sensing applications.

Suppressed Lattice Thermal Conductivity in Haeckelite Compounds for High-Performance Thermoelectric Applications.

Traditional semiconductors are known to exhibit excellent electrical properties but oversized lattice thermal conductivities, thus limiting their thermoelectric performance. Herein, we have discovered a low-energy allotrope of those traditional semiconductors. Compared with the wurtzite structure, the lattice thermal conductivity is reduced by more than five times in the haeckelite structure. This is attributed to the softening of acoustic phonon modes and concurrently enhanced anharmonicity in the haeckelite structure. Benefiting from the suppressed lattice thermal conductivity while retaining the excellent electrical properties of wurtzite structure, haeckelite compounds have been proven to be a novel category of high-performance thermoelectric materials. As an excellent representative, haeckelite CdTe exhibits a peak figure of merit approaching 1.3 at n-type doping and high temperature, which experiences a 3-fold improvement compared with its wurtzite counterpart. This work provides an alternative pathway of engineering the lattice thermal conductivities of traditional semiconductors toward superior thermoelectric properties.

Synergy of functionalized activated carbon and ZnO nanoparticles for enhancing photocatalytic degradation of methylene blue and carbaryl

This study proposes preparing ZnO and ZnO/activated carbon (AC) for photocatalytic applications. ZnO and AC were synthesized using precipitation and carbonization processes, respectively. Particle sizes of ZnO and ZnO/AC were estimated at 121–135 nm. The crystalline structure analysis confirmed the presence of hexagonal wurtzite structures in ZnO. Microcrystalline graphite and amorphous carbon structures were observed in AC. The combination of these characteristics was observed in ZnO/AC. ZnO/AC exhibited an increase in surface area from 25.36 to 29.86 m2/g and a decrease in pore diameter from 5.66 to 4.31 nm. The chemical states of ZnO and AC remained unchanged. Therefore, the nanocompound structure of ZnO/AC can be inferred. The ZnO/AC nanocompounds were then employed to degrade methylene blue (MB) dye and carbaryl (CBR) insecticide, demonstrating excellent photocatalytic performance compared to pure ZnO. The apparent degradation rate constant reached an average value of 3.49 × 10−3 and 16.25 × 10−3 min−1 for MB and CBR, respectively. AC functions as carrier collectors in the ZnO/AC nanocompound structures due to the suitable energy band level for facilitating electron and hole transfers. This results in recombination suppression and prolonged lifetime, thus enhancing photocatalytic activity. The finding suggests the potential use of ZnO/AC nanocompounds to degrade agricultural chemicals in contaminated natural water under sunlight.

Long Electrical Stability on Dual Acceptor p-Type ZnO:Ag,N Thin Films.

p-type Ag-N dual acceptor doped ZnO thin films with long electrical stability were deposited by DC magnetron reactive co-sputtering technique. After deposition, the films were annealed at 400 °C for one hour in a nitrogen-controlled atmosphere. The deposited films were amorphous. However, after annealing, they crystallize in the typical hexagonal wurtzite structure of ZnO. The Ag-N dual acceptors were incorporated substitutionally in the structure of zinc oxide, and achieving that; the three samples presented the p-type conductivity in the ZnO. Initial electrical properties showed a low resistivity of from 1 to 10-3 Ω·cm, Hall mobility of tens cm2/V·s, and a hole concentration from 1017 to 1019 cm-3. The electrical stability analysis reveals that the p-type conductivity of the ZnO:Ag,N films is very stable and does not revert to n-type, even after 36 months of aging. These results reveal the feasibility of using these films for applications in short-wavelength or transparent optoelectronic devices.